Cohabitation is easily entered into but is unlikely to lead to the altar, especially for poor and minority women. A new Cornell study reports that one-half of all cohabiting unions end within a year and 90 percent within five years, mostly because couples break up. Indeed, say the researchers, cohabitation is emerging as "an intense form of dating."

"The common view of cohabitation as a steppingstone to marriage needs to be seriously questioned," said Daniel Lichter, professor of policy analysis and management and director of the Bronfenbrenner Life Course Center, both at Cornell. "Instead, serial cohabitation may be an emerging norm as cohabiting unions form and break up.

"If marriage promotion programs hope to target poor cohabiting women, our results seemingly suggest that the likelihood of success is not assured," he added.

The study was published in the May issue of Demography.